--headless is not strictly mandatory, but you want it.
Without it, the document is still converted (note "convert /.../filename.doc -> /.../filename.txt using text" message on stdout) but an empty GUI is also started (and the command blocks until you close the GUI).

Couple of noob questions incoming.
1. that is two separate commands?
2. the first command, that looks like it is telling windows where to look for soffice.exe, or is it also looking for the files you want to convert?
3. Do I need to have command prompt open to the directory the files are in for this to work, I am guessing so.
4. If this is all entered in at the same time, do I need to separate the commands in any way?

Comments

Thank you for this - on Windows 7 I was getting unhelpful crash dialogs until I added the "start /wait" to the command. As a note the first quoted parameter for 'start' is the window name, so if you try to call the above from a script with a space in the path you may need to do it like: start /wait "" "C:\program files\libreoffice 4\program\soffice"